From industrial robots to humanoid robots, in various fields involving using robots, an actuator is generally used that has a speed reduction function for smooth joint movement.
Particularly, in robotics technology which has been developing rapidly recently, robotics mechanisms which have been conventionally applied only to industrial fields are being grafted to other fields, for example, a home cleaning robot, a programming educational robot, a robot toy, and an entertainment robot, etc.
In such robot technology, the actuator related to driving is a very important main component and includes a reduction gear as a main component.
Although there are various kinds of reduction gears, representative examples of the reduction gears may include a gear type reduction gear, a rolling ball type reduction gear, and a cycloid reduction gear, etc.
Here, the gear type reduction gear is the most used general reduction gear that uses an involute tooth form.
The rolling ball type reduction gear reduces speed by rolling a ball in a guide groove in a shape in which an epicycloid curve and a hypocycloid curve are facing each other.
The cycloid reduction gear generally obtains reduced speed by fixing a pin, eccentrically rotating a trochoid gear using an epicyclic gear and rotating only the trochoid gear using a pin hole and a pin disposed at the same angle in the trochoid.
Particularly, the cycloid reduction gear among the above described reduction gears is widely applied to a field for requiring a precise control because of a capability of realizing various reduction ratios and an advantage of high precision and a large speed reduction.
Meanwhile, FIG. 1 is a schematic view illustrating an automatic device to which a conventional reduction gear is applied, and FIG. 2 is a schematic view illustrating an output position feedback unit of the conventional reduction gear. Description will be done with reference to the drawings.
First, as illustrated in FIG. 1, an output position feedback unit (40) is additionally installed outside of a conventional reduction gear (20) in an automatic device to which the reduction gear (20) is applied, and the output position feedback unit (40) is linked to a reduction gear output unit (20b) by a power transmit unit (30) as a medium.
Furthermore, the output position feedback unit (40) and the reduction gear (20) are fixed to a body (50) of a robot, etc. by fixing parts (50a and 50b) as media.
In addition, a power source which transmits power to a reduction gear input unit (20a) mostly uses a motor (10) and is linked to the reduction gear input unit (20a) by a motor shaft (10a), and furthermore, the power source and the motor may also be linked to each other by various mechanical components such as a gear, a belt pulley, and a coupling.
In addition, as illustrated in FIG. 2, the conventional reduction gear (20) only supports a fixed type input/output method provided by a manufacturer because the output position feedback unit (40) is provided outside of the reduction gear 20 without a unit sensing an input/output position.
Accordingly, it is difficult to change the input method after the reduction gear (20) is manufactured, and since power transmitted by the reduction gear (20) cannot be controlled, and thus, information of an absolute output position and input/output displacement cannot be sensed and applied to a control of the automatic device.
In addition, since an integrated conventional reduction gear (20) is not adaptable to a driving unit having various driving types, there is a limitation to selecting an input driving unit, and thus, it is cumbersome to prepare an additional unit which connects the reduction gear (20) and the input driving unit.
Accordingly, since a structure of the reduction gear (20) becomes complex, maintenance cost such as processing cost and manufacturing cost is high, and since the entire volume of the reduction gear (20) becomes increased, there is a disadvantage in miniaturization of the reduction gear (20).